Persons who have been confined to a wheelchair whether through injury or through a condition which has affected them since birth typically spend long periods of inactivity time that could be spent exercising. Exercise would improve their strength and function and prevent the muscles that are not often used from atrophying. However, due to weakness and reduced mobility, transfers to exercise machines can be functionally difficult and often impossible without the assistance of others.
Two specific muscle groups that are difficult for a wheelchair-bound patient to exercise are the abdominal and back extensor muscle groups. It is important that a patient perform trunk flexion-extension movements on a regular basis in order to prevent the muscles from atrophying due to disuse. As it is impossible to perform these movements in a regular wheelchair, it is difficult for someone that has a very limited use of their legs and possibly their arms to exercise these very important muscle groups. A need exists, therefore, for a device which allows a person confined to a wheelchair to exercise their abdominal and back extensor muscles.
While chairs and wheelchairs having a reclining feature do exist, none of the chairs are provided with the structure of the invention for the purpose of exercising a patient's torso. A need exists, accordingly, for a device which would permit a wheelchair user to perform the required flexion-extension movements, while providing a safe, stable environment for the user. Such device should preferably provide a variable resistance to the motion to allow for users of different ability.
In the prior art, U.S. Pat. No. 4,125,269 depicts a wheelchair with a provision for the seat to rock. The seat is supported by a pair of trapezoidal linkages that allow the seat to displace forwardly and rearward. However, there is no synchronization with the back portion during this motion. Further, there is no separate resistance attached to either the flexion or extension movement.
U.S. Pat. No. 6,213,923, while not relating to a wheelchair, depicts an exercising reclining device with seat and back portions that are interlinked. The front portion of the seat both slides and rotates about a pivoting axis positioned centrally across the seat and lying directly adjacent to the underside surface of the seat. The rearward portion of the seat is pivotally linked to an extended bottom edge of the back. The back is said in the description to rotate about a shaft connected to the frame. According to the drawings, this action may occur through both a rotational and sliding hinged connection to the frame. According to the drawings, as the back reclines, the point of rotation of the back shifts downwardly. An extension from the back portion protruding below its hinged support is flexibly connected to the rear edge of the seat. A “decline control mechanism 22” is connected between the frame and the joint existing between the seat and back portions, providing either resilience or resistance to deflection (herein after a “resistance” means) within the mechanism. As the back reclines, the seat both rotates and shifts forwardly on its sliding pivot axis, sliding on its supports.
Similarly to U.S. Pat. No. 6,213,923, a reclining chair is depicted in U.S. Pat. No. 3,767,190 wherein the central portion of the seat rotates about a sliding pivot point mounted within a slot on a portion of the folding frame. The rearward portion of the seat is pivotally linked to the bottom edge of the back. The back rotates about its own, hinged connection to the frame at a location which is above the bottom edge of the back. A spring is connected between the frame and a joint connecting the seat and back portions to resist a reclining action. As the back portion reclines, the seat portion is slid and tipped forwardly, while an extension to the seat portion may protrude to underlie a user's thighs.
In U.S. Pat. Nos. 4,504,090; 5,209,549; 4,877,291; 3,947,069 and 2,512,353 each respecting a chair, but not a wheelchair, these references all provide back and seat portions which are connected so that the seat projects forwardly when the back reclines. A specific mechanism is provided to achieve this effect in each case.
In respect of U.S. Pat. No. 4,877,291 the front edge of the seat of a chair, but not a wheelchair, is supported by a swinging link which extends upwardly from the forward region of the seat to a portion of the chair frame while the reclining back pivots about a hinge point fixed to the frame. When the back reclines this seat portion advances, rising slightly along its forward edge as the swinging link departs further from a vertical alignment. A resistance mechanism is coupled between the frame and an extension to the bottom end of the back portion so as to resist the motion of the seat and back portion when the back reclines.
In U.S. Pat. No. 4,607,883 to a chair, but not a wheelchair, the reclining back pivots about a hinge point fixed to the frame. The rear edge of the seat is connected to an extension of the back protruding below the hinged support for the back so that as the seat projects forward, the back reclines. The front edge of the seat is in this case supported by rigid strut, which extends downwardly from the sides of the seat to a portion of the chair frame. The connection between this strut and the chair frame itself includes a pivoting joint connected to a sliding joint which is fitted to the frame through a kind of sliding shoe. This is said to render smoothness to the reclining action. However, as the frame portion that supports the sliding shoe is significantly inclined upwardly, forward advancement of the chair seat has a tendency to elevate the front portion of the seat. Further, this is another example of providing support for the seat through a sliding joint.
It would be desirable to provide a wheelchair adapted to provide exercise wherein all or substantially most of the resistance experienced by the user is provided through an external component not connected with the support for the seat and back.
In the foregoing references the frame for supporting the seat and back portions have been resting directly on the floor through legs or equivalent supports. In the case of a wheelchair this support is provided through wheels, and largely through the principal, large diameter wheels characteristic of most wheelchairs. While such wheels may be locked, there is always present in the case of a wheelchair the risk that a user may shift their centre of gravity backwards to a point rearwardly of the support provided by the large wheels, causing the wheelchair to tip backwards. Many wheelchairs include safety stops to accommodate this event. However, it is still undesirable for any rearward tipping to occur in a wheelchair while the user is exercising his abdominal muscles. In the design of any wheelchair wherein a user may shift his centre of gravity, it is important to minimize the risk that any rearward tipping will occur. As well as providing for an exercise mechanism, the following invention addresses that objective.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.